0ski_dwn_it

Again you guys are trying to compare apples (n/a) to oranges (forced induction)...the guy here is asking about a car that will probably rev to about 4500RPM if he is lucky.

Remember what I said about BSFC - induction motors need more fuel injector cause they mechanically make the motor more efficient - more airflow, so hence they need more injector.

Of course anything can be tuned for, but as you are seeing from other reporting in that an over injected motor need more time and TLC to get right.....but enough time can get it right. No one is argueing that point. The thought on this though, is why go through the hassle to get the same exact results.

Today Corky and I ran all day long - I ran within .1 sec of him all day long 10.5s and 10.6s (me with 30#ers) and him with 24#ers. He was quicker every run. We pulled plugs and compared...mine looked richer than his, and his were even on the rich side, just not as much. Bottom line we both have more than enough fuel to do what we need to do. These are motor running pretty damn big cams 242+ duration and super flowing heads and intakes. I was shifting at 6800 and he was at 6100. Not sure why anyone with a motor making less than 600hp would imagine they need larger than 30# injectors....the proof is in the puddling.

I logged several of my passes on the Gen7 system and the WB02 was always around 12.6-12.8.

Can I ask what the 383/SC w/50# injector car runs in the 1/4? ET/MPH?

Beach Bum

This is crazy stuff guys....

Not sure how anybody could ignore 2 forum members naturally aspirated solid roller 434's with plain old 24lb injectors in 3300 lb cars that run traps at and above 130 mph..... and I know them, they're been beating on their motors since they put them together and the only carnage they have experienced has been related to the always fun C4 IRS.... motors have been happy as can be. Their results are hard for me to ignore and my mind is as open as anybodys when it comes to this stuff.

For the members in favor of larger injectors, how would larger injectors help these 434's ? Would they go faster ? If yes, how much faster ? More reliable ? Better fuel economy ? What about the original poster with his motor.... same questions. Also, do you have any personal set-ups details and results you can share with us comparing big vs little injectors ?

I'm probably a lot like a lot of other people on this forum and that is I believe what I see... in otherwords, the proof is in the timeslip to me. Others may prefer their dyno or g-tech or seat of the pants feel as their personal gauge....not me, I, as many others look for timeslip proof.

Thanks !!
Beach Bum

Racetronix

What is your base fuel pressure?
What is your average and maximum injector DC under WOT?
What do you consider a safe injector DC?
What is your injector DC under WOT at elevated temps and lower vehicle voltage?
Does your motor benefit from a SEFI system vs. a factory ECM?
What does your car weigh?
Do you still have all your power accessories A/C, P/S, mechanical water pump etc.?
How much improvement have you made over the factory BSFC thanks to the upgrades on your intake system?
How does your BSFC compare to Strike3's given the two combos?
Does your intake provide your injectors with a straighter path to the base of your intake valve?
Which brand / type of injector are you running?
What is your actual FWHP and TQ?

If Strike3's motor has a very good BSFC and it is a low RPM combo then perhaps his minimum TTI will be such that he can use a smaller injector and still get the fuel he needs between each cycle to meet his desired A/F.

Nobody is saying he needs a 50# injector. Point is people tend to be scared of going to a slightly larger injector when they shouldn't be. If somebody thinks they are going to keep upgrading their HP why buy an injector that is just enough at the time? The point I was making with the imports and Buicks is that they usually buy an injector that will take them all the way to their ultimate HP objective. In the beginning they scale the fuel delivery back for their relatively stock combos without sacrificing mileage or drivability. As they add more go-fast goodies they simply retune the combo for more fuel. They don't generally upgrade their injectors every time they add another 50-100HP. Yes, FI on a small CID motor needs more fuel than a NA V8 making the same HP but again I am not saying he should step up to a 50# injector. Depending on his BSFC, base FP and DC he is comfortable with he may prefer something in the 30# range? Given the fact that there is little to no price difference he might consider a larger injector?

Over the years I have seen many cars where a tuner has allowed a motor to ride the 100% injector DC curve as a means for controlling the A/F under WOT. This is a practice which I can not agree with as I have seen it cause much damage time and time again. I am a firm believer that an injector must be run at 80-90% DC (depending on the type) in order to maintain stable / repeatable fuel delivery. My studies on the injector flow bench here only stand to up my position.

93 ragtop

One simple question. If 24lbs is enough then why did GM go from 24lb (LT1) injectors to 28LB injectors on the LT4?
Keep in mind this was only a 30 hp motor increase.

85vet

Simple answer with another question.
If GM's engineeers know all, why do we bother changing/modifying our cars?
This is a very old argument, similar to mini-ram vs superram, etc. Each have valid stats - the decision has to be made by the individual and there particular situation.
Just a quick note - I run Ford 24# in my 383 and I run fat at 40pounds even with jebs single plain intake that flows more air than the SuperRam. I do not have the specific wide band info other than data logs of my car.

luvmy92

Again, you always assume everyone is running the 1/4 mile. I know 8388 is into top-end, and I am into road racing. I am running 30 #'s on my 385 because my tuner said I would need them due to the long periods of time at WOT in the upper rpm band (4 - 6k). Do you feel the 24 #'s could handle that as well? I'm just curious.

Mike

0ski_dwn_it

Listen...I think beach laid it out pretty good for you guys.

I always find it humorous how on here you have the guys that "think" they know what they are doing, and then you have the guys that take flack for trying to help people out with their stuff - and have REAL world proof and results to back up their statements.

We have output some of the best running n/a motors this board has seen:

85vet 383ci 24# injectors 40# pressure 11.2@123+
Corkys 406/SR 24#injectors 38#pressure 10.91@125+
Ski's 406/SR 24#injectors 40#pressure(lowest my regulator would go) 11.02@123+mph

Corky's 434/SP 24#injectors (been on the car for 4+ years, run every weekend) 48-50# pressure 10.27@131+ MPH making easily over 600hp
Ski's 434/SP 30# injectors 40# pressure with the 251/251cam 10.3@133+MPH making high 500s/low 600s hp
Went to larger cam, bigger than some big block cams and 30# injectors are coming around, but my RPMs never drop below 6000 RPM through entire run - and I had to get a Gen7 to gain control over the engine management, since the stock ECM out of control above that and was going crazy with that cam. Had I not switched cams the 24# injectors would have been back in.

-------then some of the other great running motors on here...

Ralphs 406/SP 24# injectors (he can fill in the pressure he likes) - 10.9s ET making I would guess mid to high 500hp

Beach's 383/SR 24# injectors (again he can fill in pressure) - running bottom 11s@123+ mPH if I recall correctly.

----------------

Now why on god's green earth would you think that this guys motor that will be making around 260-300rwhp ~ 2000rpm less than any of these motors turn - need any larger injectors than 24#ers?????

At some point common sense has to kick in and say - well if these guys can successfully run 24# injectors on motors up to and over 600hp weekend after weekend, year after year - why on earth would I need bigger than them.

Its really no different than going to a track and seeing a guy with a 406ci 870 carbed motor - run in a 3300lbs car over 125+ MPH (high 500hp motor) then return home and built the same CI motor with lesser parts flowing parts and think you need a 1095 King Demon carb to top it off.

Well I agree with Beach's statement 100%, that its pretty hard to ignore that above setups success - I think you will have a pretty tough time putting together a list of equal CI range motors from this forum that are running even close to these numbers. And there are a few others like corvette0096 and others that I did not even list that too run VERY strong for their setups.

At the end of the day - this is a performance venue that guys come to for gain knowledge from others so they do not have to fight through the muck themselves to figure it out. Those that want to venture into unchartered waters and not use common sense based on what others have done successfully - well its your dime and your car - as I said before- no sweat off my brow. But I will try to help people out with seeing the light - hence why I posted here for the original posters question. I hope I am wrong, but I will bet that if he puts 30# injectors in that car, he will regret it as many other have and you have seen come on here. Not only will he be unhappy, but he will be spending another 200+ dollars - maybe more if he has someone else change then over for him. Not to mention the hassle.....

The proof is in the pudding.....

Luvmy vette - YES there is no doubt that 24# injectors would run your car just as well as larger ones do. As I said before, fuel is fuel - we can supply over 600hp motors with enough, your motor making 150-200hp less will be fine.

Again I find it humorous how people think that larger injectors somohow safeguard them from disaster...should "something" happen. Racetronix - what happens if you running 50# injectors in a road race and your fuel pump is weak and starts to fail? You will run lean and cause damage to your motor possibly if your not smart enough to leave off when it starts to surge. Same happens if your fuel filter gets clogged......

I am still waiting to hear someone come on here and show us an injector that failed from higher duty cycles - and as beach asked as well as I did, do you not think we would instantly put larger injectors in our cars if we thought/knew they would yield us more ET? I just spent nearly 2K dollars for a Gen7 to make the car go quicker hopefully with the cam I now have - I think I would spring for 200 dollar injectors if I thought it would help.

Until someone comes on here with similiar setups, running larger injectors making more power - I think our statements and advice above are pretty sound....and if someone does - I will be the first to be asking the questions to them on how they are doing it and be the first following their lead, just as I am suggesting the original poster does with the above examples.

bigcityvette

WOW...I think you are missing the point others are tying to say...either that or you are plain ignoring it.

24lb injectors are not the answer for everyone car, especially those making 400, 500, 600+ hp.

It is obvious that your above mentioned experience is based on track time only and maybe a drive to the track and back. In the real world that is not good enough. There are alot of other driving conditions that must be looked into: top end runs, road racing, commuting in every day traffic (stop, go, slow down, etc) a/c and other accessories on the motor, heat soak, and the list goes on and on and on.

Anyone that brags on some of the fastest running cars making 600+ hp on 24 lb injectors with sky high fuel pressure obviously has more to learn re: duty cycles and tuning cars for real world use and not just track use.

That is obvious by not being able to tune a solid roller cam with a gm 165 ecm and having to goto gen 7 DFI.

93 ragtop

Well GM designs the cars for a broad range of drivers, emissions, gas mileage, and reliability.
A lot of us try to trade some of these things in for more power.
GM seen a need to increase the injectors on the LT4 by 4lbs. The differences are larger valves, slightly more cam, and slightly more compression. Again, it only amounted to a 30 hp increase. Now some will argue that it is more like a 50hp increase and it may well be. But none of the less they increased the size of the injectors.
Oh, and please dont try to tell us that anyone on this board has more knowledge about corvettes then the engineering team that designed it.

Beach Bum

I don't know the answer to your question, but we could find many examples for these type questions in both directions, for example, why does Lingenfelter Performance Engineering only utilize a bosch 26lb injector for their 383 - 440 HP motors ? In actuality, due to how they rate their injectors a ford svo 24lb injector flows about the same as the bosch 26lb..... was Lingenfelter using too little injector for those 440 hp motors or is the LT-4 using too much ? (I believe bosch rates at 50 psi, whereas ford rates at somewhere around 44 psi)

My questions in my previous post were simply asking what would we gain by going to a larger injector ? I'm not going to argue with somebody who says go to a larger injector, you might be right.....but I am going to ask why.

As a note, my current motor makes in the range of 430-440 hp give or take a little, I have daily driven it in the heat of stop and go traffic in southern california for many years and it has seen literally 1000 1/4 mile passes and it has also seen extended empty highway stretches of high speeds, ie, similar to what a road racer would see. This 383 motor is now approaching 70,000 miles, with every one utilizing the same ford svo 24 lb injectors. I've never had a single problem with the motor or injectors. I think I can say with reasonable confidence, that I have not been overtaxing my 24lb injectors.... and my fuel pressure is set at close to stock 44 psi. BUT, if somebody can demonstrate to me how my motor would improve in some way by going to a 30 or 36lb injector.... I'll switch tomorrow !!

I think this is all I am asking..... what would I get?


ski, my set-up only runs 116 to 119 mph depending on air quality and track elevation. But, I'd love it to run 123 mph

cheers,
Beach Bum

85vet

Sorry if I offended the corvette gods at GM, and I never said anyone on this board knows more about engines/injector for the C4, but then maybe there is . All I am saying is - GM was not allways correct with their past decisions.

bigcityvette

I agree, GM is not always right in their past decisions. Usually it is how a car is rolled out to the public. I.E. the GrandSport was a C4 with a paint job and a LT4 motor. Great motor but nothing like the GS from the 60's and it definetly should have put out more power with a limited produciton sbc vs the LT4.

luvmy92

Just for the record, I am making 415 to the rear wheel.

All of the people you mention above are running these cars hard for no more than 12 seconds at a time. I am aware that they may be running them harder for longer periods outside of the drag strip. I would like to know if any of these same people are running them hard like that for 30 minutes at a time on a road course? If they are, I would like to hear of their experiences with the smaller injectors.

Thanks,
Mike

85vet

I too would like to hear. I know the 24's work for me, but I do agrea, they may not if I were set up for and running a road course.

FD2BLK

Ok,
So I have managed to muddle through this entire thread and there are some pints of view I don't get or agree with. I notice the question about how efficient the motors running 24# injectors with 500+ HP was never answered. There is a huge variance with injectors that will work with a given combo as long as the tuner has a clue of what they are doing. The key is to get the proper A/F ratio and still have a good duty cycle. Ski, you have a very fast car and I am glad you and Cork feel confident with your injector choice, but as far as the proof is in the pudding, I would have to say my Tuner has done faster cars then either of yours and a hell of a lot more of them. Here is a link to his +400 HP cars, (notice the 773 HP 00 Corvette that passed MD emissions.)
http://www.carolinaautomasters.com/400club.html
Before I bought the injectors for my combo I asked Jeff what he would like to see and felt he could tune the best with and he said FMS 42s but I got a great deal on the 36s and he said he could tune them with no problems as well. The point is a good tuner can work with a wide variety of injectors and still have great results. My car has perfect drivability and still gets 17 MPG going back and fourth to work in city traffic.

Mad-Mic

no offense but an LS1 pulls ALOT more CFM than any SB1 will ever dream of. this is the reason LSx based motors run bigger injectors. alot of these LSx Tuners know their stuff i will give them that but most, give them a carberated motor to tune or better yet one of our L98's and watch them struggle.

0ski_dwn_it

BigCity...Ahhh my car ran 10.33@133 with the stock GM ECM....I think that is saying that I can tune the stock ECM pretty well. Not only that but my tuning is on nearly every car I mentioned above....all of which are "fairly" respectable output power plants. Don't think I have to defend my tuning ability with anyone -

Also I am running a 296/302 264/278@.050 duration cam with a 108lsa in at 104 that is about 5 times as large as most people on here run - and larger than even some of the high 400 CI bigblocks that guys run.....so please save me the BS of not being able to tune it. When your RPM range is about 5600+ RPM through nearly the entire run, it doesn't make much sense to use an ECM that doesn't control fuel above that range in the resolution I need it to......but oh yeah you are one of the ones preaching about making sure you have enough fuel.

At the end of the day I will say it again.,...you guys that come here preaching about needing this or needing that - no different than the MAF debate - your all wet. Corky is still running MAF that was suppose to be done making power by the "experts" at 350rwhp....they also used used the same arguement that GM switched with the 90s cars that made more power - so SD has to be the ticket. Hmmm 600hp sucking through a MAF running 10.2s is more proof than I need to prove their "theories" wrong. Again I HAVE convertered to SD cause I truely thought that MAF would be done at mid 10s, but I am yet to exceed corky's best, with virtually the same exact setup. So that tells me my conversion to SD was a waste of time and money - you can either learn from it, or waste your money like I did.

And for you guys that think we are all about 1/4 mile times...again you throw your stupidity on the line. I will put my car w/ 700r4 back in it on the line against any of you guy's cars for a 3 mile straight out run anytime. Of course I will not be the one driving my car, since it should only be fair that an equally experienced driver is behind the wheel for that type of racing and to be honest I don't care to go past 180MPH for extended times. Remember my friends these cars are capable of going over 133MPH from a dead stop in 1/4 of a mile, with 3.07 gears Racing even a new z06 that leave them about 50 car lengths behind in just the 1/4 mile. What do you think top end is on one of these cars? And trust me they are pulling like freight trains at the end of a 1/4 mile run as well. The 1/4 mile is nothing but brutal acceleration - I think if the rest of the car was properly configured for a certain type of racing, their ablity to perform above average would shine in these venues as well.

At the end of the day fellas, we can argue and argue about who is right and who is wrong. But I think many see that results and real world speak louder than accusations. I am yet to hear one of you mention and example of a car that is laying down more power in similiar trim/equipment to support your claims, much less having your hand in building them. But yet you ridicule someone like myself that is always pushing the envelope and freely sharing my learning experiences to help others so they do not have to go through the same leg work. There are only a handful of guys here that R&D stuff here to the finite level we do with our stuff and critisism about moving to a DFI system is childish. The decision was nothing more than my own curiousity and drive to learn another system, and to otimize my setup once again for the recent changes I made to it - then bring back the experience to the forum to help guide others. I have to ask.....what have you done lately along those line. I know now more people are sticking with MAF than ever before, I know many people are reeping the benefits from the single plane, and countless people are modeling their setups after our past performers. I could see the critisism if we would not share our experiences and just come on here to tell people they are wrong, but that is hardly the case - and more the other way around.

Bottom line is prove me wrong by producing better results and as said above I will be the first to be taking notes and asking the questions to learn more.

To the gentleman that wants to compare the LS1 version motors to a standard 23* headed car - well again its apples and oranges. If I did as much stuff as I did to my car, to that of an LS type motor is would be running mid to low 9s, and yes it would need more injector - cause they move a LOT more air - hence make more power. But due to their design they flow more like a 18* or 15* head.

Another thing that I would like to ask, is how many of you that "preach" about needing more fuel etc, have even take the time to flow your fuel system to see how much volume is can even flow.....or did you just assume it can? I know I have....

93 ragtop

Well no offense taken by me anyways I dont know about the other gods. Just kiddin. The reason I believe he should change the injectors is his tuner says he needs them for his 413. You cant take your car to a mechanic, tell him how to fix it, and then complain. If you dont agree with his decision then switch mechanics.
The other reason I would do it is based on my own tuning experience and that is, I had Alvin at PCMFORLESS to dyno tune mine. I believe he is one of the most reputable tuners in the country IMO. Anyways I have a stock 350 short block, ported heads with bigger valves, headers and a hotcam. Well he maxed out the stock injectors and the AF is going as lean as 13.8 Alvin advised me to get 30lb svo injectors which I plan to do.
However this has been put on hold to repair my dana 44 which broke
While im at it im going to get my transmission rebuilt again since it seems to be taking longer to shift between gears.
You know how this goes. Heck I guess this is part of that reliability thing I was talking about.

FD2BLK

The LS1 was one example of well over 100 listed producing over 400 RWHP. Take a good look again; he tunes just about every car known not Just TPI non-speed density systems. Hell he tuned my friends TBI blazer with just about one of the oldest EFI ECMs out there. A good tuner can accommodate a wide variety of injectors and still tune the car correctly. If some tuners can not seem to get the hang of tuning with larger injectors and maintain drivability, and you use them, then stick with 24# FMS injectors but it doesn't make it any better then a larger injector running a better duty cycle. Agian, I think that as long as the duty cycle is fine and the A/F ratio is good then changing injectors is a waste of time.

luvmy92

Hey bub... I said nothing in my posts that would call for your calling me stupid. Quit being so sensitive.

Again, is there someone out there running the smaller injector on a stroker motor that is doing any road racing? I'm not saying it can't be done. I would just like to hear from someone that is doing it, that's all. My builder strongly recommended the 30's for this application, although he was not the one that ended up tuning my motor.

BTW, if anyone is interested, I have a set of stock injectors off my 92 that were sent to Rich at Cruzin Performance, where he cleaned and flowed them (I have the before and after sheet). They have never been used since they were cleaned. Make an offer. I'll post this on the 4-sale board as well.

Mike